Malaria Box Compounds against Anopheles gambiae (Diptera: Culicidae) Carboxypeptidase B Activity to Block Malaria Transmission

Carboxypeptidase B (CPB) plays an important role in blood digestion in mosquitos, aiding the release of free amino acids. Anopheles CPB is a target to block malaria transmission because it facilitates Plasmodium invasion of the mosquito midgut. Our study aimed to discover inhibitors of Anopheles CPB to prevent Plasmodium development in the mosquito. The Anopheles gambiae cpb (Agcpb) gene without a signal sequence was cloned into the pET28b expression vector. The recombinant AgCPB protein was expressed in E. coli BL21(DE3) within inclusion bodies after induction with 0.5 mM isopropyl β-D-1-thiogalactopyranoside at 37°C for 4 h. The protein pellet was dissolved in 6 M urea, purified by affinity chromatography, and dialyzed in reaction buffer. The refolded recombinant AgCPB could digest the hippuryl-arginine substrate similarly to that of the commercial porcine pancreas CPB. The 20 top-scoring malaria box compounds from the virtual-screening results were then chosen for an in vitro inhibition assay against AgCPB. Four of the 20 malaria box compounds could inhibit AgCPB activity. The compound MMV007591 was the most potent inhibitor with an IC50 at 0.066 µM. The results indicate that these candidate compounds may be utilized in drug development against mosquito CPB activity to curb malaria transmission.

Structure of Aedes aegypti carboxypeptidase B1-inhibitor complex uncover the disparity between mosquito and non-mosquito insect carboxypeptidase inhibition mechanism

Metallocarboxypeptidases (MCPs) in the mosquito midgut play crucial roles in infection, as well as in mosquito dietary digestion, reproduction, and development. MCPs are also part of the digestive system of plant-feeding insects, representing key targets for inhibitor development against mosquitoes/mosquito-borne pathogens or as antifeedant molecules against plant-feeding insects. Notably, some non-mosquito insect B-type MCPs are primarily insensitive to plant protease inhibitors (PPIs) such as the potato carboxypeptidase inhibitor (PCI; MW 4 kDa), an inhibitor explored for cancer treatment and insecticide design. Here, we report the crystal structure of Aedes aegypti carboxypeptidase-B1 (CPBAe1)-PCI complex and compared the binding with that of PCI-insensitive CPBs. We show that PCI accommodation is determined by key differences in the active-site regions of MCPs. In particular, the loop regions α6-α7 (Leu242 -Ser250 ) and β8-α8 (Pro269 -Pro280 ) of CPBAe1 are replaced by α-helices in PCI-insensitive insect Helicoverpa zea CPBHz. These α-helices protrude into the active-site pocket of CPBHz, restricting PCI insertion and rendering the enzyme insensitive. We further compared our structure with the only other PCI complex available, bovine CPA1-PCI. The potency of PCI against CPBAe1 (Ki  = 14.7 nM) is marginally less than that of bovine CPA1 (Ki  = 5 nM). Structurally, the above loop regions that accommodate PCI binding in CPBAe1 are similar to that of bovine CPA1, although observed changes in proteases residues that interact with PCI could account for the differences in affinity. Our findings suggest that PCI sensitivity is largely dictated by structural interference, which broadens our understanding of carboxypeptidase inhibition as a mosquito population/parasite control strategy.

Molecular characterization of carboxypeptidase B-like (CPB) in Scylla paramamosain and its role in white spot syndrome virus and Vibrio alginolyticus infection

Carboxypeptidase plays an important physiological role in the tissues and organs of animals. In this study, we cloned an entire 2316 bp carboxypeptidase B-like (CPB) sequence with a 1302 bp open reading frame encoding a 434 amino acid peptide from Scylla paramamosain. The CPB gene was expressed highly in hepatopancreas and decreased in crab hemocytes after challenges with white spot syndrome virus (WSSV) or Vibrio alginolyticus. After CPB gene knockdown using double-stranded RNA (CPB-dsRNA), the expression of JAK, STAT, C-type lectin, crustin antimicrobial peptide, Toll-like receptors, prophenoloxidase, and myosin II essential light chain-like protein were down-regulated in hemocytes at 24 h post dsRNA treatment. CPB knockdown decreases total hemocyte count in crabs indicated that CPB may negatively regulate crab hemocyte proliferation in crabs. CPB showed an inhibitory effect on hemocyte apoptosis in crabs infected with WSSV or V. alginolyticus. The phagocytosis rate of WSSV by hemocytes was increased after CPB-dsRNA treatment. After WSSV challenge, the mortality and WSSV copy number were both decreased but the rate of hemocyte apoptosis was increased in CPB-dsRNA-treated crabs. The results indicate that the antiviral activity of the crabs was enhanced when CPB was knocked down, indicating WSSV may take advantage of CPB to benefit its replication. In contrast, the absence of CPB in crabs increased mortality following the V. alginolyticus challenge. The phagocytosis rate of V. alginolyticus by hemocytes was increased after CPB-dsRNA treatment. It was revealed that CPB may play a positive role in the immune response to V. alginolyticus through increasing the phagocytosis rate of V. alginolyticus. This research further adds to our understanding of the CPB and identifies its potential role in the innate immunity of crabs.

Crystal structure of mutant carboxypeptidase T from Thermoactinomyces vulgaris with an implanted S1' subsite from pancreatic carboxypeptidase B

A site-directed mutagenesis method has been used to obtain the G215S/A251G/T257A/D260G/T262D mutant of carboxypeptidase T from Thermoactinomyces vulgaris (CPT), in which the amino-acid residues of the S1' subsite are substituted by the corresponding residues from pancreatic carboxypeptidase B (CPB). It was shown that the mutant enzyme retained the broad, mainly hydrophobic selectivity of wild-type CPT. The mutant containing the implanted CPB S1' subsite was crystallized and its three-dimensional structure was determined at 1.29 Å resolution by X-ray crystallography. A comparison of the three-dimensional structures of CPT, the G215S/A251G/T257A/D260G/T262D CPT mutant and CPB showed that the S1' subsite of CPT has not been distorted by the mutagenesis and adequately reproduces the structure of the CPB S1' subsite. The CPB-like mutant differs from CPB in substrate selectivity owing to differences between the two enzymes outside the S1' subsite. Moreover, the difference in substrate specificity between the enzymes was shown to be affected by residues other than those that directly contact the substrate.

Biomarkers allow detection of nutrient limitations and respective supplementation for elimination in Pichia pastoris fed-batch cultures

BACKGROUND

Industrial processes for recombinant protein production challenge production hosts, such as the yeast Pichia pastoris, on multiple levels. During a common P. pastoris fed-batch process, cells experience strong adaptations to different metabolic states or suffer from environmental stresses due to high cell density cultivation. Additionally, recombinant protein production and nutrient limitations are challenging in these processes.

RESULTS

Pichia pastoris producing porcine carboxypeptidase B (CpB) was cultivated in glucose or methanol-limited fed-batch mode, and the cellular response was analyzed using microarrays. Thereby, strong transcriptional regulations in transport-, regulatory- and metabolic processes connected to sulfur, phosphorus and nitrogen metabolism became obvious. The induction of these genes was observed in both glucose- and methanol- limited fed batch cultivations, but were stronger in the latter condition. As the transcriptional pattern was indicative for nutrient limitations, we performed fed-batch cultivations where we added the respective nutrients and compared them to non-supplemented cultures regarding cell growth, productivity and expression levels of selected biomarker genes. In the non-supplemented reference cultures we observed a strong increase in transcript levels of up to 89-fold for phosphorus limitation marker genes in the late fed-batch phase. Transcript levels of sulfur limitation marker genes were up to 35-fold increased. By addition of (NH4)2SO4 or (NH4)2HPO4, respectively, we were able to suppress the transcriptional response of the marker genes to levels initially observed at the start of the fed batch. Additionally, supplementation had also a positive impact on biomass generation and recombinant protein production. Supplementation with (NH4)2SO4 led to 5% increase in biomass and 52% higher CpB activity in the supernatant, compared to the non-supplemented reference cultivations. In (NH4)2HPO4 supplemented cultures 9% higher biomass concentrations and 60% more CpB activity were reached.

CONCLUSIONS

Transcriptional analysis of P. pastoris fed-batch cultivations led to the identification of nutrient limitations in the later phases, and respective biomarker genes for indication of limitations. Supplementation of the cultivation media with those nutrients eliminated the limitations on the transcriptional level, and was also shown to enhance productivity of a recombinant protein. The biomarker genes are versatily applicable to media and process optimization approaches, where tailor-made solutions are envisioned.

Active Compounds Against Anopheles minimus Carboxypeptidase B for Malaria Transmission-Blocking Strategy

Malaria transmission-blocking compounds have been studied to block the transmission of malaria parasites, especially the drug-resistant Plasmodium. Carboxypeptidase B (CPB) in the midgut of Anopheline mosquitoes has been demonstrated to be essential for the sexual development of Plasmodium in the mosquito. Thus, the CPB is a potential target for blocking compounds. The aim of this research was to screen compounds from the National Cancer Institute (NCI) diversity dataset and U.S. Food and Drug Administration (FDA)-approved drugs that could reduce the Anopheles CPB activity. The cDNA fragment of cpb gene from An. minimus (cpbAmi) was amplified and sequenced. The three-dimensional structure of CPB was predicted from the deduced amino acid sequence. The virtual screening of the compounds from NCI diversity set IV and FDA-approved drugs was performed against CPBAmi. The inhibition activity against CPBAmi of the top-scoring molecules was characterized in vitro. Three compounds-NSC-1014, NSC-332670, and aminopterin with IC50 at 0.99 mM, 1.55 mM, and 0.062 mM, respectively-were found to significantly reduce the CPBAmi activity.

CPB1 of Aedes aegypti interacts with DENV2 E protein and regulates intracellular viral accumulation and release from midgut cells

Aedes aegypti is a principal vector responsible for the transmission of dengue viruses (DENV). To date, vector control remains the key option for dengue disease management. To develop new vector control strategies, a more comprehensive understanding of the biological interactions between DENV and Ae. aegypti is required. In this study, a cDNA library derived from the midgut of female adult Ae. aegypti was used in yeast two-hybrid (Y2H) screenings against DENV2 envelope (E) protein. Among the many interacting proteins identified, carboxypeptidase B1 (CPB1) was selected, and its biological interaction with E protein in Ae. aegypti primary midgut cells was further validated. Our double immunofluorescent assay showed that CPB1-E interaction occurred in the endoplasmic reticulum (ER) of the Ae. aegypti primary midgut cells. Overexpression of CPB1 in mosquito cells resulted in intracellular DENV2 genomic RNA or virus particle accumulation, with a lower amount of virus release. Therefore, we postulated that in Ae. aegypti midgut cells, CPB1 binds to the E protein deposited on the ER intraluminal membranes and inhibits DENV2 RNA encapsulation, thus inhibiting budding from the ER, and may interfere with immature virus transportation to the trans-Golgi network.

Activated thrombin activatable fibrinolysis inhibitor levels are associated with the risk of cardiovascular death in patients with coronary artery disease: the AtheroGene study

BACKGROUND

Thrombin activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis. Results on the association between TAFI levels and the risk of coronary artery disease (CAD) are inconsistent.

OBJECTIVES

We investigated the association between TAFI levels and the risk of cardiovascular events in CAD.

PATIENTS/METHODS

1668 individuals with angiographically proven CAD at baseline were followed for a median of 2.3 years, as part of the prospective AtheroGene cohort. Fifty-six deaths from cardiovascular (CV) causes and 35 non-fatal CV events were observed.

RESULTS

At baseline, three TAFI measurements were available: one evaluating the total amount of TAFI (t-TAFI), one measuring the TAFIa/TAFIai amount, and the last the released activated peptide (TAFI-AP). TAFIa/TAFIai levels were associated with increased risk of CV death [hazard ratio (HR) for one tertile increase, 2.38 (1.56-3.63); P < 10(-4)]. This association remained significant after adjustment for conventional risk factors, CRP levels, white blood count and markers of thrombin generation and fibrinolysis [HR = 1.69 (1.07-2.67); P = 0.01]. In addition, CPB2 gene polymorphisms explained 12%, 6%, and 3% of t-TAFI, TAFIa/TAFIai and TAFI-AP levels, respectively, but none was associated with CV events.

CONCLUSIONS

The amount of activated TAFI, measured by TAFIa/TAFIai ELISA, but not of the t-TAFI is independently associated with the risk of CV death.

High-level secretory expression of human procarboxypeptidase B by Fed-Batch cultivation of Pichia pastoris and its partial characterization

The procpb gene encoding human procarboxypeptidase B (proCPB, GeneBank access code AJ224866) was cloned and its Pichia expression plasmid, pPIC9alpha/hproCPB (9.2 kb), was constructed, in which procpb was under the control of the AOX1 promoter and connected to the downstream of the mating factor alpha-1 (MFalpha1) signal sequence. The plasmid was linearized by digestion with SacI, and integrated into the genome of P. pastoris strain GS115. By culturing of Pichia transformant on methanol medium, the human proCPB was successfully expressed and secreted into the culture supernatant. Moreover, Western blot analysis of the extracellular proteins showed proCPB bands clearly at a molecular mass of 45 kDa, confirming the expression of proCPB with its right size. The CPB activity reached about 3.5 U/ml and 12.7 U/ml in the flask and fermentor batch cultures of Pichia transformant, respectively. No CPB enzyme activity was found in the intracellular fraction. When the fedbatch cultivation was performed with methanol and glycerol mixture as a feeding medium, the extracellular CPB activity was increased to 42.0 U/ml, which corresponds to a 3.3-fold higher level of CPB activity than that of batch culture. The Km and kcat values of recombinant human CPB enzyme for hippuryl-L-Arg as a substrate were estimated to be 0.16mM and 11.93 sec-1, respectively.

Carboxypeptidase B and other kininases of the rat coronary and mesenteric arterial bed perfusates

We describe the enzymes that constitute the major bradykinin (BK)-processing pathways in the perfusates of mesenteric arterial bed (MAB) and coronary vessels isolated from Wistar normotensive rats (WNR) and spontaneously hypertensive rats. The contribution of particular proteases to BK degradation was revealed by the combined analysis of fragments generated during incubation of BK with representative perfusate samples and the effect of selective inhibitors on the respective reactions. Marked differences were seen among the perfusates studied; MAB secretes, per minute of perfusion, kininase activity capable of hydrolyzing approximately 300 pmol of BK/min, which is approximately 250-fold larger amount on a per unit time basis than that of its coronary counterpart. BK degradation in the coronary perfusate seems to be mediated by ANG I-converting enzyme, neutral endopeptidase 24.11-like enzyme, and a dl-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid-sensitive basic carboxypeptidase; coronary perfusate of WNR contains an additional BK-degrading enzyme whose specificity resembles that of neurolysin or thimet oligopeptidase. Diversely, a des-Arg(9)-BK-forming enzyme, responsible for nearly all of the kininase activity of MAB perfusates of WNR and spontaneously hypertensive rats, could be purified by a procedure that involved affinity chromatography over potato carboxypeptidase inhibitor-Sepharose column and shown to be structurally identical to rat pancreatic carboxypeptidase B (CPB). Comparable levels of CPB mRNA expression were observed in pancreas, liver, mesentery, and kidney, but very low levels were detected in lung, heart, aorta, and carotid artery. In conclusion, distinct BK-processing pathways operate in the perfusates of rat MAB and coronary bed, with a substantial participation of a des-Arg(9)-BK-forming enzyme identical to pancreatic CPB.

Profiling of differentially expressed genes in hepatopancreas of white spot syndrome virus-resistant shrimp (Litopenaeus vannamei) by suppression subtractive hybridisation

In order to find immune-relevant factors responsible for virus resistance and response to the virus infection, the suppression subtractive hybridisation method was employed to identify differentially expressed genes and their expression profiles in the hepatopancreas of the white spot syndrome virus (WSSV) resistant and susceptible Pacific white shrimp (Litopenaeus vannamei). Two forward subtractive libraries (at 0 and 48h time point) and two reverse subtractive libraries (at 0 and 48h time point) were constructed, and more than 1200 clones were sequenced, of which 40 differentially expressed genes were identified. These genes encode proteins corresponding to a wide range of functions, including defence-related proteins, enzymes, transcription factors, apoptotic-related proteins, intracellular components potentially related to signaling cascades, metabolic proteins, and cytoskeletal protein. Five genes (laccase, carboxypeptidase B, H(+)-transporting ATP synthase, Acyl-ConA-binding protein (ACBP), and cortical granule protein with LDL-receptor) are found for the first time in shrimp and their expressions were up-regulated in the virus-resistant shrimp. Among the 40 genes, 30 showed up-regulation in the virus-resistant shrimp comparing with susceptible shrimp, while 10 genes showed down-regulation. Haemocyanin was the most abundant gene in our forward subtractive libraries. In addition, chathepsin L, ecdysteroid regulated protein, zinc proteinase, lectin, sterol carrier protein-X, lysozyme, cortical granule protein with LDL-receptor, leucine-rich repeat LGI family, fatty acid binding protein, and preamylase all showed up-regulation in the resistant shrimp. Furthermore, a number of genes encoding apoptotic-related proteins and antioxidant enzymes were expressed at a higher level in the virus-resistant shrimp. The high expression of the immune-relevant genes in response to the virus infection provides a new insight for further study in the shrimp innate immunity.

Carboxypeptidases B of Anopheles gambiae as targets for a Plasmodium falciparum transmission-blocking vaccine

Anopheles gambiae is the major African vector of Plasmodium falciparum, the most deadly species of human malaria parasite and the most prevalent in Africa. Several strategies are being developed to limit the global impact of malaria via reducing transmission rates, among which are transmission-blocking vaccines (TBVs), which induce in the vertebrate host the production of antibodies that inhibit parasite development in the mosquito midgut. So far, the most promising components of a TBV are parasite-derived antigens, although targeting critical mosquito components might also successfully block development of the parasite in its vector. We previously identified A. gambiae genes whose expression was modified in P. falciparum-infected mosquitoes, including one midgut carboxypeptidase gene, cpbAg1. Here we show that P. falciparum up-regulates the expression of cpbAg1 and of a second midgut carboxypeptidase gene, cpbAg2, and that this up-regulation correlates with an increased carboxypeptidase B (CPB) activity at a time when parasites establish infection in the mosquito midgut. The addition of antibodies directed against CPBAg1 to a P. falciparum-containing blood meal inhibited CPB activity and blocked parasite development in the mosquito midgut. Furthermore, the development of the rodent parasite Plasmodium berghei was significantly reduced in mosquitoes fed on infected mice that had been immunized with recombinant CPBAg1. Lastly, mosquitoes fed on anti-CPBAg1 antibodies exhibited reduced reproductive capacity, a secondary effect of a CPB-based TBV that could likely contribute to reducing Plasmodium transmission. These results indicate that A. gambiae CPBs could constitute targets for a TBV that is based upon mosquito molecules.

[Expression, purification and characterization of rat procarboxypeptidase B in Pichia pastoris]

Carboxypeptidase B is a metalloenzyme, which is widely used for commercial and research purposes. Commercially available CPB purified from porcine or bovine pancreas is very expensive, and is not totally free from other proteases. In order to express the rat proCPB in Pichia pastoris, total RNA extracted from SD rat pancreas cells was reversely transcripted to synthesize cDNA, and the proCPB ORF was synthesized by PCR. After digestion with Xho I and EcoR I , the fragment was inserted into pPIC9, and the recombinant plasmid was named as pPIC9-proCPB. By digestion with Sac I , the lined pPIC9-proCPB was transformed into Pichia pastoris strains GS115 with PEG1000 and integrated into their genomes. In the inducement of methanol, recombinant proCPB was successfully expressed in Pichia pastoris, and could be secreted into the supernatant in the culture. After optimizing the fermentation conditions, a higher production could be obtained when GS115-proCPB was induced in BMGY (pH6.0) at 28CC, with addition of 0.5% casein. The yield of recombinant protein reached 500mg/L, achieving over 94% of total protein in the culture supernatant. The purity of recombinant CPB can reach 96% after two step phenyl sepharose F F purification, and 38% of total protein can obtained after optimizing the pufication method. Comparing to the specific activity 180u/mg of CPB purchased from Sigma, the specific activity of recombinant CPB is 110u/mg. Mass spectrometry analyses showed the mass of the recombinant CPB was 35.1 kD, which is very close to the theory value 35.2 kD. Amino acid sequencing of N-terminal of recombinant CPB further indicated proCPB was expressed successfully and modificated correctly after translation.

Thrombin-activatable procarboxypeptidase B regulates activated complement C5a in vivo

Plasma procarboxypeptidase B (proCPB) is activated by the endothelial thrombin-thrombomodulin [corrected] complex. Activated proCPB [corrected] (CPB) functions as a fibrinolysis inhibitor, but it may play a broader role by inactivating inflammatory mediators. To test this hypothesis, C5a-induced alveolitis was studied in wild-type (WT) and proCPB-deficient mice (proCPB-/-). C5a-induced alveolitis, as measured by cell counts and total protein contents in bronchoalveolar lavage fluids, was markedly enhanced in the proCPB-/- mice. E229K thrombin, a thrombin mutant with minimal clotting activity but retaining its ability to activate protein C and proCPB, attenuated C5a-induced alveolitis in WT but not in proCPB-/- mice, indicating that its beneficial effect is mediated primarily by its activation of proCPB. Lung tissue histology confirmed these cellular inflammatory responses. Delayed administration of E229K thrombin after the C5a instillation was ineffective in reducing alveolitis in WT mice, suggesting that the beneficial effect of E229K thrombin is due to the direct inhibition of C5a by CPB. Our studies show that thrombin-activatable proCPB, in addition to its role in fibrinolysis, has intrinsic anti-inflammatory functions. Its activation, along with protein C, by the endothelial thrombin-TM complex represents a homeostatic response to counteract the inflammatory mediators generated at the site of vascular injury.

The renaturation of procarboxypeptidase B by urea gradient gel filtration and some properties of recombinant carboxypeptidase B

A new pro-carboxypeptidase (pCPB) gene was cloned by RT-PCR from SD rat pancreas and its overexpression in Escherichia coli resulted in the formation of inclusion bodies (IBs). The IBs of pCPB were solubilized in 8 M urea and successively refolded by urea gradient gel filtration. Subsequently, the renatured pCPB was digested by trypsin. Recombinant active CPB was obtained by passing through DEAE-FF ion exchange and Sephadex-G100 chromatographic column. Capillary electrophoresis assay showed that the purity of the recombinant CPB (rCPB) exceeded 90%. Further, some properties of rCPB were characterized. The optimum of activity was achieved at pH 7-9. The activity of rCPB was inhibited by typical metal chelating agents (EDTA) and Hg2+, and was activated by Co2+ and heat treatment at 40 degrees C. The two-dimension electrophoresis map of rCPB showed that the pI value of rCPB was 5.35. UV absorbance spectrum of the enzyme showed that an absorbance maximum was at 277 nm.

cpbAg1 encodes an active carboxypeptidase B expressed in the midgut of Anopheles gambiae

We previously used differential display to identify several Anopheles gambiae genes, whose expression in the mosquito midgut was regulated upon ingestion of Plasmodium falciparum. Here, we report the characterization of one of these genes, cpbAg1, which codes for the first zinc-carboxypeptidase B identified in An. gambiae and in any insect. Expression of cpbAg1 in baculovirus gave rise to an active enzyme, and determination of the N-terminal amino acids confirmed that CPBAg1 contains a signal peptide and a pro-peptide, typical features of digestive zinc carboxypeptidases. cpbAg1 mRNA was mainly produced in the mosquito midgut, where it accumulated in unfed females and was rapidly down-regulated upon blood feeding. Annotation of the An. gambiae genome predicts twenty-three sequences coding for zinc-carboxypeptidases of which only two (cpbAg1 and cpbAg2) are expressed at a significant level in the mosquito midgut.

Characterization and cDNA cloning of midgut carboxypeptidases from Trichoplusia ni

Carboxypeptidase A and carboxypeptidase B activities from the midgut of Trichoplusia ni larvae were characterized. In the T. ni larval midgut, the primary digestive carboxypeptidase activity was attributed to carboxypeptidase A, which was eight times more active than carboxypeptidase B. Both the midgut carboxypeptidase A and carboxypeptidase B exhibited maximal activities at pH 8.0-8.5 and were similarly susceptible to inhibition by potato carboxypeptidase inhibitor and phenanthroline. The midgut carboxypeptidase activities were analyzed in T. ni larvae fed on various diet sources and the results indicated that midgut carboxypeptidase activities per milligram of gut were similar regardless of the amount of dietary proteins or amino acids. However, midgut carboxypeptidase A activity was significantly higher in larvae exposed to soybean trypsin inhibitor and was significantly lower in larvae fed on broccoli foliage. From the T. ni larval midgut, five putative carboxypeptidase cDNAs were cloned, demonstrating that midgut carboxypeptidase activities are composed of multiple carboxypeptidase types. Sequence analysis indicated that the midgut carboxypeptidases were produced as secreted proenzymes which could be activated after removal of an N-terminal activation fragment by a trypsin. Two cloned cDNAs are predicted to code for carboxypeptidase A and one cDNA is predicted to code for a putative carboxypeptidase B. The other two cDNAs are highly similar to carboxypeptidase A and carboxypeptidase B in sequences, but their activity was not predictable.

Cloning and Expression of a New Rat Procarboxypeptidase B Gene in Escherichia Coli and Purification of Recombination Carboxypeptidase B

A new coding sequence of the procarboxypeptidase B gene was obtained from SD rat fresh pancreas by RT-PCR and highly expressed in Escherichia coli in inclusion bodies. The folded procarboxypeptidase B was subjected to trypsin enzymatic cleavage to produce active carboxypeptidase B, subsequently, carboxypeptidase B was effectively purified with anion exchange chromatography DEAE-FF and hydrophobic interaction chromatography Octyl FF, as a result, 40 mg carboxypeptidase B per litre cell culture with specific activity 7.42 u/mg was achieved. Further research showed that the obtained recombinant carboxypeptidase B could substitute carboxypeptidase B isolated from pancreas.

Impaired healing of cutaneous wounds and colonic anastomoses in mice lacking thrombin-activatable fibrinolysis inhibitor

Plasmin and other components of the plasminogen activation system play an important role in tissue repair by regulating extracellular matrix remodeling, including fibrin degradation. Thrombin-activatable fibrinolysis inhibitor (TAFI) is a procarboxypeptidase that, after activation, can attenuate plasmin-mediated fibrin degradation by removing the C-terminal lysine residues from fibrin, which play a role in the binding and activation of plasminogen. To test the hypothesis that TAFI is an important determinant in the control of tissue repair, we investigated the effect of TAFI deficiency on the healing of cutaneous wounds and colonic anastomoses. Histological examination revealed inappropriate organization of skin wound closure in the TAFI knockout mice, including an altered pattern of epithelial migration. The time required to completely heal the cutaneous wounds was slightly delayed in TAFI-deficient mice. Healing of colonic anastomoses was also impaired, as reflected by decreased strength of the tissue at the site of the suture, and by bleeding complications in 3 of 14 animals. Together, these abnormalities resulted in increased mortality in TAFI-deficient mice after colonic anastomoses. Although our study shows that tissue repair, including re-epithelialization and scar formation, occurs in TAFI-deficient mice, TAFI appears to be important for appropriate organization of the healing process.

Molecular cloning and cDNA sequence analysis of carboxypeptidases A1, A2 and B from the Japanese flounder Paralichthys olivaceus

Although pancreatic serine proteases have been cloned in teleosts, no sequence data are currently available on members of the carboxypeptidase (CP) family. Here, we cloned cDNAs coding for two preproCPAs, corresponding to mammalian preproCPA1 and preproCPA2, and one preproCPB from a pancreatic cDNA library of the Japanese flounder, Paralichthys olivaceus. The activation peptides of flounder proCPs completely retained the sequences for inhibition of enzymatic activity of proCPs just like mammalian proCPs. Of 306-309 amino acids in total, 95 amino acids are completely conserved between bovine CPA1 and CPB and flounder CPs. Notably, amino acid residues for Zn(2+) ligands, catalysis and substrate anchoring are completely conserved between flounder and bovine CPs. Three species of flounder preproCPs are all expressed in the pancreas of first feeding larvae.